1. Field of the Invention
The subject invention relates to apparatus and methods for enclosures of the type that are used in the installation and maintenance of electrical and electronic equipment and, more specifically, methods and apparatus for preassembly and installation of subterranean enclosures of the type that are used in communications networks.
2. Description of the Prior Art
Communications systems have been under continual development for many years. More recently, developments relating to various communication media, including fiberoptic, microwave, and electrical networks, have accelerated the rate at which communications systems as well as other information and control systems are being revised and improved.
To utilize these continued advances in technology, it has become necessary for both users and providers of these systems to more frequently update and improve the system components. This has resulted in more frequent and often more technically complex modifications and improvements than have been previously required. The increasing complexity of communications systems and other affected systems and the somewhat delicate nature of the system components also has made installation of the system improvements increasingly more complex and costly. Moreover, the environment in which many installations must be made has often made such field installations more vulnerable to human errors and component failures.
Accordingly, the prior art has included various attempts to curtail the cost and difficulty associated with the installation of complex or physically delicate communications systems. Such attempts have included various designs and methods for constructing enclosures to house the communications systems. Protecting the systems in this way makes them less vulnerable to difficulties and complications of the type that frequently arise in field construction and assembly of such systems. These designs and methodologies include those in which substantial portions of the assembly are completed in a more controlled environment such as a fabrication or assembly shop and the assembled portion shipped to the construction site for final installation.
With particular regard to communications systems, one improvement has been the use of turndown pads in connection with the assembly and installation of new or replacement communications systems. Specifically, a turndown pad was developed that would provide for the mechanical, electrical, and optical connection of various communications systems components. In particular, the turndown pads provided for connections between a digital loop carrier cabinet ("DLC cabinet") which provides digital telephone services, a "power pedestal" which connects the main power service to the DLC cabinet, and a "cross-connect panel" which connects the telephone service from the DLC to individual telephone customers. The turndown pad allowed the most complex and difficult interconnections between the DLC cabinet, the power pedestal, and the cross-connect panel to be installed inside the turndown pad at an assembly shop. The turndown pad was then delivered to the job site where it was mechanically joined with the DLC cabinet, the power pedestal, and the cross-connect panel. Thus, the only connections that were required in the field were the splices and cutovers that were required between the cabinets and the cutovers that were required with respect to inputs and outputs to the network.
One difficulty with the prior turndown pad system arose in part from the fact that there are a number of suppliers of the various cabinet components of the network, but there is no standardization for the dimensions and configurations of the various cabinets. This has meant that the electrical interconnections and the mechanical connections that are required to secure the cabinets to the turndown pad vary in accordance with the particular cabinets and combination of cabinets that are used at a particular installation. The diversity between cabinets is such that no standardized or universal connection has been developed in the prior art. The number and variety of available cabinets is sufficiently large that a great number of possible combinations of cabinets exist. This in turn has required that, to control inventory costs of the turndown pads, the turndown pads have been fabricated on a made to order basis.
Another difficulty with some prior turndown pads has been that they were fabricated out of concrete. Fabricating concrete turndown pads on a made to order basis has required significant fabrication time. The concrete forming process is relatively slow and is inherently limited by the rate at which the concrete will cure. Concrete turndown pads are also relatively heavy and therefor somewhat difficult and unsafe to transport and manipulate. Typically, such concrete turndown pads weigh approximately 22,000 pounds or more.
More recently, improvements were made by which the turn down pads could be prefabricated and assembled at a fabrication shop and thereafter transported to the installation site with the cabinets already mounted thereon. These improved turn down pads were made of composite materials such that they had strength and the rigidity sufficient to support the various cabinets, but also were lighter and more easily moved and manipulated than the concrete turndown pads that were known in the prior art. Also, these turndown pads could be assembled from pre-fabricated components such that the finally assembled turndown pad could be constructed more rapidly and with greater flexibility than the prior turndown pads.
These improvements greatly decreased construction time and cost for turndown pad fabricators and users, thereby also reducing the cost and installation time for the communication system. However, further improvements to the apparatus and methods for fabricating turndown pads whereby inventory requirements would be further controlled and simplified could further reduce costs and promote still further flexibility and responsiveness in the construction of the turndown pads.